Treatment of cast iron



Patented Feb. 13, 1951 TREATMENT OF CAST IRON Harry B. Kinnear and George P. Krumlauf, Co-

lumbus, Ohio, assignors, by mesne assignments, to Chromium Mining & Smelting Corporation, Limited, Sault Ste. Marie, Ontario, Canada, a corporation of Ontario No Drawing.

Application November 14, 1945,

Serial No. 628,664

12 Claims.

This invention relates to metallurgy and has for an object the provision of certain improvements in metallurgical methods or processes. More particularly, the invention contemplates the provision of certain improvements in methods or processes suitable for use in the production of cast iron. A particular object of the invention is to provide an improved method or process for improving the mechanical or physical properties of cast iron. A specific object of the invention is to provide a method or process for treating cast iron to improve its mechanical or physical properties.

The invention is based on our discovery that cast iron can be treated while in the molten state with a nitrate to produce cast iron products hav ing improved mechanical or physical properties. Thus, for example, we have found that by reacting with a nitrate, molten cast iron, such as cupola iron and blast furnace iron, containing not less than about two and one-half percent (2.5%) of carbon and about one per cent (1.0%) of elemental silicon, cast iron products having improved transverse, tensile, deflection, impact, hardness and other properties can be produced. The method or process of the invention is particularly useful for treating gray cast iron to improve its properties. The use of nitrate for treating cast iron in accordance with the invention has little or no effect on the depth of chill.

In carrying out a method or process of the invention, molten cast iron from any suitable source is reacted in a ladle, for example, with a nitrate in amount sufiicient to modify the mechanical or physical properties or characteristics of the cast iron without altering substantially the composition of the cast iron with respect to carbon and silicon. The percentage of carbon in the cast iron may be altered about 0.03 to 0.06 percent, or about 1 to 2 percent of the actual carbon content, and the percentage of silicon in the alloy may be altered about 0.06 to 0.13 percent, or about 4 to 7 percent based on the actual amount of silicon present in the cast iron.

Any suitable nitrate may be employed in carry-- ing out a method of the invention. A single nitrate may be employed in treating a bath of molten cast iron, or the bath of molten cast iron may be treated with two or more nitrates singly or in admixture. Nitrates of sodium, strontium, barium, calcium and copper may be employed with particular advantage in carrying out a method or process of the invention. The nitrates may be employed in any suitable amounts which by reaction with the cast iron will not seriously alter the composition of the cast iron with respect to carbon and silicon. We have employed nitrates in amounts by weight equal to about four-tenths of one percent (0.4%) to about one and one-quarter percent (1.25%) of the weight of the cast iron treated.

The following examples illustrate results obtained in carrying out methods or processes of the invention employing various nitrates in the amounts in treating in ladles sixty pound batches of molten cast llOIl. products of the compositions indicated:

W M f Metal Analyses eig 0 1 352? Addition,

Lb. Per Cent Per Cent Per Cent Per Cent '1. Mn Si N No addition- 3. 15 l 54 1. 002 NaNOs 0.50 3.12 .50 1.41 .009 Ba (NO3)z 0.50 3.14 52 l. 44 009 020 addition- 3. 25 56 1. 6l 003 NaNO; 0. 50 3. 21 51 l. 52 008 Ba(NOa)2 0. 50 3. 24 54 l. 57 008 Si(NO3)2 0. 50 3. 19 52 l. 51 .011 No additioiL 3.15 1.88 .002 Nal'FIOg 0.25 3.14 1.84 .004 D0 0.50 3.12 1.80 005 D0 75 3.12 1.75 005 CA(N 3)2 50 3. O9 1.84 .008 {o additiom 3. 29 l. 58 .004 haNOanufl 25 3. 28 1. .006 D0 50 3. 27 l. 52 006 Cu(NOs)z. 50 3. 27 l. 56 .006 Ca(NO3)z .50 3.25 1.52 .Oll

Mechanical Properties of Test Bars Weight of Reagent Added Addition,

Lb Trans- Tensile, Deflecverse, Lb. per tion,

Lb. Sq. In. Inches Noaddition 2, 760 37, 450 305 Nab, O3. 0. 50 3, 180 43, 450 207 Ba(NO3)z 0. 50 3, 040 42, 300 300 No addition 2, 570 38, 250 292 NaNO3- 0. 50 3, 250 50, 075 323 Ba (NOa)2- 0.50 3,065 46, 650 .312 Sr(NO3) z 0.50 3,155 48, 250 297 No addition. 2, 690 36, 350 .299 NaNO3 0. 25 3, 005 39, 450 331 Do 0. 50 3, 085 41, 150 304 Do 75 3,185 40, 900 .340 Ca(l TOa)2 50 3, 080 38, 550 329 No addition- 2, 825 37, 500 322 l\ aNOa. 25 3, 048 41, 500 322 Do 50 3, 240 43, 900 .320 0110103) 50 3, 125 42, 700 312 Oa(NO3)2 50 3, 215 43,350 280 Weight of 1111 B. H. N.

pact, Chill, Reagent Added Aliglglon, 300321155. Inches N0 addition 45.50 0. 50 52. 00 0. 50 52. 00 43. 50 0. 50 55. 60 0. 50 52. 0. 50 55. 00 49.00 0. 25 56. 00 0. 50 58. 75 75 59. 50 50 57. 25 51. 50 25 58. 00 50 65. 00 50 53. 00 50 59. 00

3 We claim? 1. The method of treating cast iron which comprises reacting the cast iron while molten.

modify the mechanical or physical characteristics or properties of the cast iron;

2. The method of treating cast iron which comprises reacting the cast ironiwl'iilamoltenzwithz one or more nitrates including sodium nitrat'e in' amount by weight equal to about four-tenthsofone percent (0.4%) to about one and one-quarter percent- (1.25%). of: the weight of .the. cast iron and sufiicient to modify. the; mechanical'or .physir cal characteristicsor properties of! the castiron.

3. The method-of treating cast iron which .comprisesreacting'the cast ironwhile molten with one or more nitrates including strontiumnitrate in amount by weight equal to about four-tenths of one percent (0.4%) to about one and onequarter percent (1.25%) of the weight of the cast iron and sufficient to modify themechanical or physical characteristics or properties of the cast iron.

4. Themethod of treating cast iron which comprises reacting the cast iron while molten with one or more nitrates including barium'nitrate in amountby weight equal to about four-tenths. of one percent (0.4%) to about one and one-quarter percent (1.25%) of theiweight of'the cast iron and sufficient to modify the mechanical or physical characteristics or'properties of the. cast iron.

5. The method of treating cast iron containing not less than'two and one half percent of carbon and one. percent of elemental silicon which comprises" reacting the cast iron while molten with one or more nitrates in amount by weight equal'to about four-tenths of'one percent (0.4%) to about one and one-quarter percent (1.25%) of the weight of the cast iron and sufficient, to modify the mechanical or physical characteristics or properties of the cast iron,

6. The method of treating cast iron containing not'less than two and'one-halfpercent' of carbon andone percent'of elemental silicon which comprises'reacting the cast ironwhilemolten with one or more nitrates including sodium nitrate in amount by weight equalto about .fourtenths of onepercent (0.4%) to about one. and one-quarter percent (125%) of the weight of the cast iron and sufficient to' modify'the mechanical or physical characteristicsor properties of the cast iron.

7. The method of treating cast iron containing not less than two and one-half percent of carbon and one percent of elemental silicon which comprises reacting the cast iron while molten with one or more nitrates including strontiumnitrate in amount by weight equal to about four-tenths of one percent (0.4%) to about one and one-quarter percent (1.25%) of the weight of the cast iron andsufiicient'to modify the mechanical or physical characteristics or properties of the cast iron.

8iThe= method of treatingjcast 'ii'on contain ing not less than two and one-half percent of carbon and one percent of elemental silicon which comprises reacting the cast iron while molten with one or more nitrates including barium nitrate inamount-byweight equal to about fourtenthssofi onezpercent (0.4%) to about one and one-quarter'percent (1.25%) of the weight of the-cast 'iron'andsufficient to modify the mechanical'orphysica'l characteristics or properties ofithe castiirorn 9. The method of treating gray cast iron which comprises reacting the cast iron While molten with one or more nitrates in amount by weight equallto aboutfour-tenths of one percent (0.4%) to. about one and'one-quarter percent (1.25%) of the weight of the cast ironandsufficient' to modify the mechanical or physical characteristics or properties of the cast iron.

10. The method of' treatingv gray cast iron which comprises reacting the cast iron while molten with one or more nitrates including sodium nitrate in amount by weight equal to about four-tenths ofone. percent (0.4%.) to about one and one-quarter percent (1.25%) of the weight of thecast iron andsuificient to modify the mechanical or physical"characteristicsor properties of the cast iron.

11. The method of treating, gray cast iron which comprises-reactingthe cast iron while molten with one or more nitrates including strontium nitrate in amount by weight equal to about four-tenths of one percent (0.4%) to about one and one-quarter'percent? (1.25%) of the weight'of'the castliron and sufficient" to modify the mechanical or physical characteristics or properties of the. cast iron;

12. The method of treating gray cast iron which comprises reacting, the. cast' iron while molten with one or. more nitrates including barium nitrate in amount by weight equal to about four-tenths of one percent (0.4%) to about one and one-quarter percent (1.25%) of" the weightiof thecast iron and sufficient to modify the mechanical or physical characteristics or properties of the cast iron;

HARRY B. KINNEAR. GEORGE'P. KRUMLAUF.

REFERENCES CITED Thefollowingreferences are of record-in the file. of thispatent-:-

UNITED STATES PATENTS" Number Namev Date.

412,443. Archbold .Oct. 8, 1889 6'61;406 Leiby Nov. 6,.1900

2,174,740 Graham et al Oct. 3, 1939 2,243,783 Udy May 27, 1941' 2,280,872 Udy, Apr. 28, 1942 2,339,673 Boegehold Jan. 18, .1944

FOREIGN PATENTS.

Number Country Date 798 Great Britain Of 1866 

1. THE METHOD TREATING CAST IRON WHCIH COMPRISES REACTING THE CAST IRON WHILE MOLTEN WITH ONE OR MORE NITRATES IN AMOUNT BY WEIGHT EQUAL TO ABOUT FOUR-TENTHS OF ONE PERCENT (0.4%) TO ABOUT ONE AND ONE-QUARTER PERCENT (1.25%) OF THE WEIGHT OF THE CAST IRON AND SUFFICIENT TO MODIFY THE MECHANICAL OR PHYSCIAL CHARACTERISTICS OR PROPERTIES OF THE CAST IRON. 